Process design and intensification for the clean separation of ternary multi-azeotropes system via special distillation coupled with reaction

Abstract

A ternary mixture of diisopropyl ether, isopropanol and water exists in the production process of isopropanol. Ensuring the clean separation of this mixture is of great significance for the clean production of isopropanol from both economy and environment. However, there are three binary and one ternary minimum boiling point homogeneous azeotropes in this system, which complicate the clean production of isopropanol. In this study, with the aid of the hydration reaction of ethylene oxide, clean separation of a ternary mixture of diisopropyl ether–isopropanol–water was realized. Three separation processes—reaction–pressure swing distillation, reaction–extractive distillation and reaction–dividing wall extractive distillation—were proposed. These processes were optimized based on the sequential iterative algorithm, with the minimum total annual cost as the objective. Reaction-pressure swing distillation had the best economic performance, reaction-extractive distillation followed, and reaction-dividing wall extractive distillation performed the worst. The carbon dioxide, sulfur dioxide, and nitrogen oxide emissions of the three processes were calculated based on the optimization results. Reaction-pressure swing distillation had the lowest emissions, followed by reaction-dividing wall extractive distillation. However, reaction-extractive distillation had the highest emissions. The exergy analysis of distillation units and exchanger was performed, and the results showed that reaction-pressure swing distillation had the best exergy performance. Reaction-pressure swing distillation was better than reaction-extractive distillation and reaction-dividing wall extractive distillation in terms of economy, environment, and thermodynamic efficiency. This study provides an original idea for the clean separation of diisopropyl ether-isopropanol-water azeotropes.